Not noticed any blurring on ITV HD. BBC HD due to, lets face it, low bit rate effect (Clues in the name HD!, keep the information please, please!)Think ITV's 'scaled' standard def stuff is excellent. Channel 5's is too. Get to watch 'Thomas the Tank Engine' in psuedo HD with the little one.
As for adverts im guessing they may be slightly brighter too, 'Showroom effect' trying to get you're attention.
Regards,
Cookie Monster